While conventional soft-switching attempts exist in various technical literature, there are inherent issues limiting the use of those conventional designs in commercial systems. These limitations include conduction and reverse recovery of metal-oxide-semiconductor field-effect transistor (MOSFET) body and conventional diodes, insulated-gate bipolar transistor (IGBT) tail currents, and parasitic inductance and capacitance of all circuitry components present in the conventional designs.
Some attempts to address these issues have included designs employing fast-switching (more expensive) wide bandgap devices such as silicon carbide (SiC) transistor devices in lieu of slower (less expensive) IGBT devices. Other attempts to address the aforementioned issues have included single-cycle control schemes that extrapolate, during a single cycle, values of a voltage across a switch so as to estimate a time at which to soft switch moments later during the same cycle. The extrapolation techniques, however, cannot accurately estimate the ZVS timing because observed values of the voltage typically include spurious noise compromising the extrapolation and because of inherent delays between the switch being activated and its actual time at which it is conductive. The inaccurate estimates, therefore, actually indicate a time where hard switching or body diode conduction losses would occur.